2017 Asia-Pacific Engineering and Technology Conference (APETC 2017) ISBN: 978-1-60595-443-1 Sulfonation and Application of A Polysaccharide as High Inhibitive Drilling Fluid Additive Xue-Fan Gu, Qiang Zhang, Chao Cheng, Jie Zhang and Gang Chen

ABSTRACT

To improve the solubility of a kind of plant polysaccharide derivative (SJ) in drilling fluid system, it was modified by sulfonation with sodium 3-chloride-2-hydroxy-propyl sulphonate (CHPS) as sulfonating reagent. The reaction conditions were investigated by orthogonal designed experiments, and the optimized conditions were as follows: the mass ratio of CHPS to SJ is 0.6g/1g with pH 12 at the temperature of 90℃. The viscosity of sulfonated SJ (SJS) drilling fluid system was greatly improved and the temperature had a slight effect on rheological properties below 120℃. The inhibitive property of SJS is evaluated by clay-swelling tests and the mud ball immersing tests, which is obviously stronger than SJ and even more effective than 4wt% KCl solution.1

INTRODUCTION During the well drilling process, drilling fluid additives are widely used to control the rheological property and filtrate of muds [1]. Now days, natural polymers are preferred over synthetic materials due to their properties of low pollution, low cost, non-toxicity and biodegradability[2-4]. A series of plant polysaccharides have been used as drilling fluid additives such as xanthan gum, guar gum, cellulose and starch [5,6]. SJ is a kind of plant polysaccharide derivative produced from the resin of Prunus persica L. Batsch. The SJ macromolecule is a straight chain basically joined by aldopentose and aldohexose, and it is composed of L-arbinose (42.8%), D-galactose (35.7%), D-xylose (14.3%) and D-sedoheptulose (7.2%). With good viscosity increasing property, shear stability, biodegradability and good compatibility, it can be used as eco-friendly drilling fluid additives [7]. However, the low solubility of SJ has limited its use. Chemical modifications have been tried to improve its solubility in water based drilling fluid. The aim of the present paper is to report the sulfonation of SJ and its properties as a kind of drilling fluid additive.

Xue-Fan Gu, Qiang Zhang, Chao Cheng, Jie Zhang*, Gang Chen College of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an 710065, China [email protected] 1

2074 EXPERIMENT

NaHSO3 solution in flask with three necks was lowly added epichlorohydrin (ECH) for 2 hours and at the temperature of 85℃. The molar ratio of NaHSO3 to ECH is 1.15:1, and the mixture was heated at certain temperatures for 1.5 hours. Then, the system was cooled to room temperature in ice water bath. After vacuum filtration, the residue was recrystallized to give sodium 3-chloride-2-hydroxy-propyl sulphonate (CHPS). SJ, NaOH and water were mixed and stirred at certain temperature until a homogeneous gel was formed. A certain amount of CHPS was then added. The mixture was heated at certain temperatures for a few hours, and the pH was adjusted with sodium hydroxide (10wt%). After completion of the reaction, the gel was cooled to room temperature and the pH was adjusted to 7~9 with dilute hydrochloric acid. After solvent distilled off under reduced pressure, the residue was dried and crushed over 120 mesh sieve to give the modified product (SJS). The chemical equation is shown in Scheme 1.The reaction conditions were investigated by orthogonally experiments test and the performances of the modified product in drilling fluid were investigated. O SO3Na + NaHSO Cl SO3Na Cl 3 OH OH

NaOH H H H H O O HO OH H H O H O H O O OH HO O HO O H OH H HO H H O OH H H H H O H HO OH H HO H H HO H HO H n HO H H H OH H H H H HO H OH HO H H OH n Scheme 1. Sulfonation of SJ.

RESULTS AND DISCUSSION According to our previous study, four factors including the temperature (A), the pH (B), the reaction time (C) and the mass ratio of CHPS to SJ (D) have the most significant effects on the modification. In order to obtain the optimal synthesis conditions, each factor has been matched with three levels as shown in Table 1. 4 Orthogonal experiments have been designed according to the standard L9 (3 ) table as shown in Table 2. The reactions are evaluated by the rate of apparent viscosity increase of drilling fluids treated by modified products.

Table 1. The three level of each factor. Mass ratio of CHPS Factor Temperture (A) pH (B) Reaction time (C) to SJ (D) Level 1 50℃ 8 4h 0.1 Level 2 70℃ 10 8h 0.3 Level 3 90℃ 12 12h 0.6

The reaction conditions can be optimized by orthogonal experiments, and the influence relationship of four factors was gotten through analysis of range. As it showed in Table 2, the range shows that the temperture has the greatest impact on the

2075 sulfonation, follows by the pH, the mass ratio of sulfonating agent to SJ and the reaction time. The optimized conditions were as follows: the mass ratio of CHPS to SJ is 0.6g/1g with pH 12 at the temperature of 90℃.

4 Table 2. Experimental results and analysis table of orthogonal design l9 (3 ).

Factor No. AV Increases % A B C D 1# 1 1 1 1 5.20 10.64 2# 1 2 2 2 5.95 26.60 3# 1 3 3 3 7.50 59.57 4# 2 1 2 3 5.45 15.96 5# 2 2 3 1 5.95 26.60 6# 2 3 1 2 6.50 38.30 7# 3 1 3 2 7.05 50.00 8# 3 2 1 3 7.95 69.15 9# 3 3 2 1 7.35 56.38 K1 96.81 76.59 118.08 93.63 K2 80.85 122.34 98.94 114.9 K3 175.53 154.26 136.17 144.69 R 94.68 77.67 37.23 51.06

The rheological properties and filtrate of sulfonated SJ (SJS) treated drilling fluids have been tested. Compared with SJ, SJS with a concentration of 0.3wt% remarkably increased the viscosity of base mud a by 69.15%, and reduced the filtration loss with a percentage of 30.6%. With the optimized reaction conditions, the SJ was modified, and the product suspending in water was shown in Figure 1. It can be found that before modification, SJ is hard to resolve or suspend in water, most of which precipitates t the bottom of the bottle. After modification, SJS is well dispersed or resolved in water, which makes a uniform liquid. Based on this test, it can be concluded that sulfonation of SJ can enhance the water solubility, which may be useful for the performance in water-based drilling fluid.

Figure 1. The suspension of SJ(left) and SJS(right).

Drilling fluids treated by SJS were aged for 16h at different temperatures from 25℃ to 180℃. As shown in Figure 2, both the apparent viscosity and plastic viscosity decreased with temperature increasing at the range of 25℃~120℃; but the variety of apparent viscosity has an opposite trend with that of plastic viscosity with temperature increasing at the range of 120℃~180℃. While the filtration loss of

2076 drilling fluids increased gradually with temperature increasing at the range of 25℃~120℃ but increased dramatically with temperature increasing at the range of 120℃~180℃. Compared to SJ, the temperature resistance of SJS decreased slightly. The fact may be due to the increased solubility of SJS and more stable cross linking effect with clay as the temperature goes on. When the temperature was increased successively, the rheological property and filtration loss became worse significantly, to a large extent, which because the enhancement of the repulsive force between the anions and the hydrogen bond more easily damaged. [10]. 12 40

35 10 AV PV 30 8 FL 25

6 FL/mL

AV,PV/mPa·s 20

4 15

2 10 0 25 50 75 100 125 150 175 200 Temperature /℃ Figure 2. The temperature resistence of SJS (0.5% wt.).

The mud ball immersing tests provide a more intuitive way to describe the inhibitive property of SJS gum. The mud ball was immersed into water, 4wt% KCl solution, 0.5wt% SJ solution and 0.5wt% SJS solution, respectively. Figure 3 shows the status of the mud balls after immersed for 48 hours. The mud ball immersed in water cracks obviously, but slightly SJ solution, but hardly in 4wt%. KCl solution. In SJS solution, the mud ball immersed swelled slightly and the surface was very smooth with no cracks.

Figure 3. The status of mud balls immersed into water, 4wt% KCl solution, 0.5% wt. SJ solution and 0.5wt% SJS solution for 48 h.

The inhibitive property was evaluated by clay-swelling tests at normal temperatures and pressures. The linear expansion rates were shown in Figure 4. The generic cores made by bentonite were immersed into distilled water, 4 wt% KCl solution, 10% wt. Na2SiO3 solution, 0.3wt% SJ solution, 0.3wt% SJ solution, 0.3% wt. SJS solution and 0.5% wt. SJS solution for 3h, respectively. It was shown that the linear expansion rate of the clay was 75.14%, 56.71%, 72.83%, 58.58%, 56.71%, 47.68% and 34.99%, respectively. Obviously, the swelling rate of SJ solution

2077 enhanced with its concentration increasing. Moreover, the swelling rate of both 0.3% wt.SJ solution and 0.5% wt. SJ solution were more effective than that of Na2SiO3 solution but lower than that of 4% wt. KCl solution. While, the swelling rate of both 0.3wt% SJS solution and 0.5wt% SJS solution were significantly improved and also enhanced with their concentration increasing. The inhibitive property of SJS may be due to their special structure. A large number of hydroxyl groups combined with the clay surface by hydrogen bond which formed a hydration shell on the clay surface, blocks the water penetration into the clay and prevent clay from further hydrating swelling. The hydrophilic sulfonic acid groups of the modified products can weaken the hydrogen bonding interaction in the molecular chain, improved the water solubility of SJS and form a diffused double layer, which makes the clay particles stability in drilling fluid [2-4].

80 70 Blank 60 4% KCl 50 10% Na2SiO3 40 0.5% SJ 30 0.3% SJ

Swelling ratio/% 20 0.5% SJS 10 0.3% SJS 0 0 20 40 60 80 100 120 140 160 180 Time/min Figure 4. The linear expansion rate of the clay in different solutions.

The particle size distribution of montmorillonite in water, SJ suspension and SJS suspension is tested to realize the interaction between SJ/SJS and montmorillonite. It can be seen from Figure 5 that the SJ can inhabit montmorillonite hydration so that the particle size is much larger than that of the blank test. When SJS was added before montmorillonite hydration, the particle size of montmorillonite is slightly reduce diminish, and the particle size is much larger than that of SJ, which can be attribute to the high absorption of SJS on montmorillonite by the abundant hydroxyl groups.

Figure 5. The particle size distribution of montmorillonite in water, SJ suspension and SJS.

2078 CONCLUSION To improve the solubility of a kind of plant polysaccharide derivative (SJ), it was modified by sulfonation. The modification conditions of SJS were screened, and the optimal conditions were as follows: the mass ratio of CHPS to SJ is 0.6g/1g with pH 12 at the temperature of 90℃. The viscosity of SJS drilling fluid system was greatly improved and the temperature had a slight effect on rheological properties below 120℃. Clay-swelling tests show that SJS has significantly stronger clay inhibition in the water-based drilling fluids.

ACKNOWLEDGMENT This work was financially supported by the grants from National Science Foundation of China (No.50874092), Industrial Science and Technology Research Projects of Shaanxi Provincial (No. 2016GY-218) and Doctor Innovation Fund of Xi'an Shiyou University (2015BS15)..

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